1. Field of the Invention:
This invention relates in general to alarms used to waken or keep one awake, and in particular, to such devices that can be worn on the head to detect the nodding of the head when one is engaged in an activity that requires the maintenance of an alert status.
2. Description of the Prior Art:
There have been several devices in the past that have been used to keep one awake or alert, especially during monotonous activities such as driving, where there is a likelihood that one may fall asleep. These devices often are designed to attach to the user's head to detect tilting or nodding of the head that often occurs when one begins to fall asleep while in an upright position.
The prior art devices have commonly employed mercury switches that rely on the flow of mercury that results from changes in the position of the head. Such a device is described in the published French patent application No. 137,910, filed Apr. 7, 1980. The flow of mercury actuates an electrical warning device that creates an audible alarm or vibration that can be detected by the user when in a drowsy or sleeping state, thus prompting them awake. While the mercury switches may be effective, the mercury used for such switches is highly toxic. As a result the use of mercury switches has been curtailed in preference of safer devices.
What is therefore needed is a device that can be used to awaken or prevent one from falling asleep by detecting tilting or movement of the user's head and which does not employ a mercury switch for detecting such motion.